Diene based polymers having low viscosity can be used without solvents to make coatings and related compositions as disclosed in several United States Patents. For unsaturated 1,3-butadiene polymers it is known that high 1,4-addition obtains low viscosity as taught in U.S. Pat. Nos. 4,518,753 and 3,652,732. However, when the polymers described in these patents are hydrogenated the products are crystalline solids. Such a crystalline hydrogenated diene polymer having terminal hydroxyl groups is available from Mitsubishi and is designated POLYTAIL H polymer which has a melting point of 72.degree. C.
The hydrogenated butadiene polymers are non-crystalline when the 1,4-addition of butadiene is below 70% as stated in U.S. Pat. No. 4,020,125. The non-crystalline hydrogenated butadiene polymers are viscous liquids at low molecular weights as described in U.S. Pat. Nos. 4,866,120 and 4,020,125. POLYTAIL HA polymer produced by Mitsubishi and NISSO GI-2000 polymer produced by Nippon Soda are commercial examples of low molecular weight hydrogenated butadiene polymers which have terminal hydroxyl groups and 1,4-addition of about 16%.
Star polymers having three or more polymeric arms of a diene connected to a central nucleus are known in the art as described in Canadian Patent No. 716,645 and U.S. Pat. No. 3,985,830. The star polymers are also useful as low viscosity components for coatings as evidenced by the fact that several diene polymers described in Example 3 of U.S. Pat. No. 3,652,732 are inherently mixtures of star diene polymers and linear diene polymers. The star diene polymers facilitate crosslinking of the diene polymers. However, the diene polymers have at least 80% 1,4-addition and are crystalline solids after hydrogenation.
The termination of living anionic polymers to form functional end groups useful for adhesives, sealants, and coatings is described in U.S. Pat. Nos. 4,417,029, 4,518,753, and 4,753,991. Capping of anionic polymers with hydroxyl, carboxyl, amine, epoxy, and phenolic groups is known. Of particular interest for the present invention are diene polymers having terminal functional groups for production of coatings.
It is an object of the present invention to provide star diene polymers having terminal functional groups and low viscosity at room temperature. It is also an object of the invention to use the low viscosity polymers to make coatings and other high molecular weight polymers.